If one power supply fet blew you absolutely have to replace all of the power supply fets. If you only replace the burnt one it may very well fail again on power up. Those fets are all connected in parallel so they all saw the same abuse. That was just the first one to give out. I think on the db-r website they say ballpark figure for repair on these is like 110-135 plus shipping which isn't bad at all when you consider what they are doing.